Conceptual Design of A 1-2 GeV Synchroton Radiation Source Page: 3 of 7
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CONCEPTUAL DESIGN OF A 1-2 GeV SYNCHROTRON RADIATION SOURCE*
The 1-2 GeV Synchrotron Radiation Source Design Staff
Lawrence Berkeley Laboratory
University of California
Berkeley, California 94720, USA
Presented by M. CornacchiaAbstract
A description is presented of the conceptual design of
the Lawrence Berkeley Laboratory 1-2 GeV Synchrotron
Radiation Source, which is designed to produce ultraviolet
and soft x-ray radiation. The facility consists of an
injection system (linac plus booster synchrotron), a low
emittance storage ring optimized at 1.5 GeV, several
insertion devices (wigglers and undulators) located in the
storage ring straight sections, and beam lines from the
insertion devices and bending magnets. Storage ring
performance is analyzed in terms of lattice, collective
instabilities and beam lifetime. The injection system and its
performance are discussed. Spectral characteristics of the
radiation are presented.
1. Introduction
The Lawrence Berkeley Laboratory has designed a
synchrotron radiation facility for the production of
high-brightness photon beams In the energy range from a
few eV to several keV. The 1-2 GeV Synchrotron Radiation
Source consists of low-emittance storage ring optimized for
insertion devices and for operation at 1.5 GeV. Eleven
straight sections are available for undulators and wigglers,
and up to 48 photon beam lines may ultimately emanate
from bending magnets. Design features of the storage ring
are the very low horizontal electron beam emittance
(4x10-9w m-rad, rms value), the short bunch length
(20-50 ps, rms value), and the tunability of the radiation.
The design accommodates the requirements of a broad range
of scientific disciplines, including atomic and molecular
physics, biology and medicine, chemical dynamics, materials
and surface science, and industrial research and technology.
2. General Description of the Facility
The 1-2 GeV Synchrotron Radiation Source consists of
an injection system (linac plus booster synchrotron), a
low-emittance storage ring optimized at 1.5 GeV (maximum
energy 1.9 GeV), several insertion devices located in thestorage ring straight sections, and beam lines from the
insertion devices and bending magnets. The major
parameters of the Light Source are given in Table 1.
Lattice Design and Single Particle Dynamics
The layout of one of the storage ring superperiods is
shown in Fig. 1. Each superperiod has reflection symmetry
around a central dipole and consists of a "dispersive region",
where the bending occurs, matched to a straight section,
6.75 m long, reserved for undulators, wigglers, injection
hardware and radio-frequency cavities. The straight
sections are dispersion free, and the optics functions are
optimized for brightness. The lattice achieves a very small
emittance (4x10- w m-rad) with moderate focusing. This
structure, called a "triple-bend achromat" because it
incorporates three bending dipoles per superperiod, was
first proposed by G. Vignola for a 6-GeV light source.'
Figure 2 shows the lattice functions in a superperiod
of the accelerator. Figure 3 gives the momentum-
dependent tune shifts. The momentum acceptance of the
lattice, of the order of t4% in Ap/p, gives a Touschek
lifetime of the order of 18 hours when the ring is filled with
a current of 400 mA. Only two families of sextupoles are
required for chromaticity correction.
The dynamic half-aperture of the machine is 23 mm in
the horizontal plane (at Bx = I I'm) and 10 mm in the
vertical plane (at By = 4 m). The presence of magnetic
imperfections in the magnets reduces the dynamic aperture
to 18 mm horizontally and 9 mm vertically. This aperture is
comfortably larger than the minimum needed for multiturn
injection in the radial plane and for a long beam lifetime.
RF Choice and Collective Effects
The achievement of short bunches is a design goal of
the Light Source, since this is a very desirable feature for
many users. In practice, the attainable bunch length is
determined by the rf parameters and the constraints of the
longitudinal microwave instability. A high frequency favors
short bunches, and for this reason, 500 MHz was chosen.0F1 OF1
01 BQ 01
B 760 1 2
4 6
Scale (meters)8
10
x8L 865 6231
Fig. 1. One unit cell of the TBA structure.
"This work is supported by the Office of Basic Energy Sciences of the U.S. Department of Energy under Contract No.
DE-AC03-76SF00098.
1
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St, The 1-2 GeV Synchrotron Radiation Source Design. Conceptual Design of A 1-2 GeV Synchroton Radiation Source, article, August 1, 1986; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc885889/m1/3/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.